Anna-Britta Hörnfeldt

The effect of some additives on the Stille Pd0-catalyzed cross-coupling reaction

Abstract It has been found that the addition of cupric oxide to the cross-coupling reaction (Stille reaction) of 2-tributylstannylpyridine with various halobenzenes and heterocyclic halides leads to a much faster reaction and higher yields. This is also the case for the formation of thieno[3,2-h]-1,6-naphthyridine from 2-(2-trimethylstannyl-3-pyridyl)-1,3-dioxolane and t-butyl-N-(2-bromo-3-thienyl)carbamate.

Palladium-catalyzed coupling of heteroaryl alkylstannanes with heteroaryl halides in the presence of silver(I)oxide

Abstract The Pd-catalyzed coupling of heteroaryl trialkylstannanes with a variety of heteroaryl halides has been shown to be greatly promoted by silver(I)oxide

Synthesis and antiviral activity of various 5-substituted 2'-deoxyuridines and -cytidines

Abstract 5-Cyclopropyl-2′-deoxycytidine and some 5-aryl-2′-deoxyuridines and -cytidines have been prepared and their inhibition of HIV have been tested.

The Crystal and Molecular Structure of Delta9-Tetrahydrocannabinolic Acid B.

The crystal and molecular structure of the title compound C-22H-30O-4, has been determined by X-ray methods using 1106 reflections above background level collected by counter methods. The crystals are orthorhombic, space group P2-12-12-1 with cell dimensions a equals 16.514(2) A; b equals 14.324(2) A; c equals 8.744(1) A; there are four molecules per unit cell. The structure was refined to an R of 0.084 (weighted R-w equals 0.068). The cyclohexene and the pyran part of the molecule occurs in the half-chair conformation. The bond distances and angles, and a slight twist of the benzene ring, indicate considerable stains in the aromatic system. Both the phenolic and carboxylic group are significantly out of the plane through the aromatig ring. The angle between this plane and a plane through the cyclohexene ring is 37.7 degrees. The pentyl sidechain occurs in an extended gauche conformation, and the thermal parameters of this part of the molecule are very high. The molecules are held together by van der Waals forces in the c-directions, and hydrogen bonds (2.688 A) from phenolic to carboxylic groups in the a-b plane. There is a short ultra-molecular hydrogen bond (2.490 A) from the carboxylic group to the pyran oxygen.

SYNTHESIS OF MIXED OLIGOMERIC HETEROARYLENES CONTAINING FURAN, THIOPHENE, AND SELENOPHENE RINGS; THEIR UV SPECTRA AND OXIDATION POTENTIALS

Abstract Mixed oligomeric five-membered heteroarylenes 3a-f and 4a-e have been prepared by cross-coupling reaction of the Grignard reagents 2 derived of the appropriately substituted thiophenes 1 with either the 2-bromoheteroarylenes or the 2,5-dibromoheteroarylenes derived of furan, thiophene, and/or selenophene respectively. The UV spectra and oxidation potential of compounds 3a-f and 4a-e are discussed on the basis of co-planarity.

Synthesis and Antiviral Activity of Carbocyclic 5-Substituted Uridines and Cytidines

Abstract Some carbocyclic uridines and cytidines have been prepared in a palladium-catalyzed reaction between 5-substituted uracils and cytosines and diacetoxymethylcyclopentene, prepared in a Prins reaction. The antiviral activity of the nucleoside analogues have been tested.

Synthesis of benzo[c]-2,7-naphthyridines by palladium-catalyzed coupling of pyridine methylstannanes with ortho bromoacetanilides in the presence of copper(II)oxide

Abstract Derivatives of benzo[c]-2,7-naphthyridine have been prepared in fair to excellent yields and in one step by the Pd(0)-catalyzed cross-coupling of pyridine methylstannanes with ortho bromoacetanilides. The coupling is greatly promoted by the addition of copper(II)oxide.

Kinetics of the reactions of some 5-bromo-2-nitro-3-R-thiophens, 3,4-dibromo-2-nitro-5-R-thiophens, 3-bromo-2-nitro-5-R-thiophens, and 2-bromo-3-nitro-5-R-thiophens with nucleophiles in methanol

The reactivity of some 5-bromo-2-nitro-3-R-thiophens (la–g; R = H, Me, Et, Prn, n-hexyl, Pr1, and But), 3,4-dibromo-2-nitro-5-R-thiophens (IIa and b; R = H and Me), 3-bromo-2-nitro-5-R-thiophens (IIIa and b; R = H and Me), and 2-bromo-3-nitro-5-R-thiophens (IVa and b; R = H and Me) with amines and sodium benzenethiolate has been studied in-methanol at various temperatures. Piperidinodebromination of compounds (la and c) has also been studied in benzene, in dioxan, and in dioxan-water (60 : 40 and 10 : 90). Independent of the position of the alkyl group (meta or para with respect to the leaving bromine), an unexpected alkyl activation has been observed, which represents a further exception to the electron-releasing behaviour of alkyl groups.

Synthesis of mixed oligomeric heteroarylenes containing thiophene and selenophene rings; their U.V. spectra and oxidation potentials

Mixed oligomers containing thiophene and selenophene rings have been synthesized; their u.v. spectra and oxidation potentials determined and discussed in terms of coplanarity of the rings and the +I-effect of the methyl substituent.

On the Synthesis of Chloro Derivatives of Five-Membered Heterocyclics via the Lithium Derivatives

Abstract In connection with our 13C NMR investigations we were interested in obtaining pure samples of 2- and 3-chlorofuran and 2- and 3-chloroselenophene. While direct chlorination with molecular chlorine or other chlorinating agents can successfully be used for the preparation of 2-chlorothiophene,1 we could not reproduce either yields or isomeric purity in the corresponding chlorination of selenophene.2,3